Best Paid Traffic source to give away free offer. Which is the best in this list?

What is the Best Paid Traffic source to give away free offers. One of my visitors to my internet tools business directory ask this question.

We all know the obvious answers of Google Adwords, Bing and Facebook but are they the best? But these are expensive source of traffic to do a free offer. What are the best high targeted low cost traffic driving sites?

What is your experience with the warrior forum?

Below are a list from my research what is your experience with them?


Best Sites

AdClickMedia - AdClickMedia Advertising Network - Pay Per Click Advertising, online text advertising, banner advertising, and Interstitial advertising.
Bidvertiser - BidVertiser - Pay Per Click Advertising On Sites Of Your Choice.
Adknowledge - Adknowledge.com | The leading long tail marketplace
Findit-quick - Pay Per Click | Pay Per Click Advertising | PPC | PPC Advertising | Pay


Media Buy Traffic Sources

Casale Media - Casale Media - Home
Valueclick - http://www.valueclick.comhttp://www....ickformula.com
Tribal Fusion - Home « Tribal Fusion
Traffiq - http://www.trafficq.com
Yahoo AdReady - AdReady - Online Display Advertising Campaign Software for Agencies, Advertisers & Publishers | AdReady
Ask - http://www.ask.com/products/
GoTraffic.com - Online traffic marketplace, where website owners and online marketers do business.
Advertising.com - Shopping Search | Ask.com
BuySellAds - Buy Ads | BuySellAds
DoubleClick - DoubleClick: The technology foundation for digital advertising
Burst Media - BURST MEDIA
Dashboard Ad - Dashboard Ad
Adengage - AdEngage - Engaging Internet Advertising
CPX Interactive - Welcome to CPX

MORE
Looksmart - LookSmart > Pay-Per-Click Search Advertising
7Search - 7Search | Pay-Per-Click Search Engine Advertising Network
Facebook Ads - Advertising | Facebook
MyAds - http://www.myads.com
Clicksor - Contextual Online Advertising and Behavioral Marketing Company
Marchex - Marchex : Pay Per Click
Adblade - Adblade - Online Advertising and Monetization Services
Adbrite - adBrite Exchange
AdSonar - http://www.adsonar.com
POF Ads - https://ads.pof.com